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Belmonte M, Ganeshan H, Huang J, Belmonte A, Inoue S, Velasco R, Acheampong N, Ofori EA, Akyea-Mensah K, Frimpong A, Ennuson NA, Frempong AF, Kyei-Baafour E, Amoah LE, Edgel K, Peters B, Villasante E, Kusi KA, Sedegah M. Immunodominant T cell peptides from four candidate malarial antigens as biomarkers of protective immunity against malaria. Vaccine 2023; 41:1265-1273. [PMID: 36642628 DOI: 10.1016/j.vaccine.2023.01.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 01/05/2023] [Accepted: 01/07/2023] [Indexed: 01/15/2023]
Abstract
A malaria vaccine with high efficacy and capable of inducing sterile immunity against malaria within genetically diverse populations is urgently needed to complement ongoing disease control and elimination efforts. Parasite-specific IFN-γ and granzyme B-secreting CD8 + T cells have been identified as key mediators of protection and the rapid identification of malaria antigen targets that elicit these responses will fast-track the development of simpler, cost-effective interventions. This study extends our previous work which used peripheral blood mononuclear cells (PBMCs) from adults with life-long exposure to malaria parasites to identify immunodominant antigen-specific peptide pools composed of overlapping 15mer sequences spanning full length proteins of four malarial antigens. Our current study aimed to identify CD8 + T cell epitopes within these previously identified positive peptide pools. Cryopreserved PBMCs from 109 HLA-typed subjects were stimulated with predicted 9-11mer CD8 + T cell epitopes from P. falciparum circumsporozoite protein (CSP), apical membrane antigen 1 (AMA1), thrombospondin related anonymous protein (TRAP) and cell traversal for ookinetes and sporozoites (CelTOS) in FluoroSpot assays. A total of 135 epitopes out of 297 tested peptides from the four antigens were experimentally identified as positive for IFN-γ and/or granzyme B production in 65 of the 109 subjects. Forty-three of 135 epitopes (32 %) were promiscuous for HLA binding, with 31 of these promiscuous epitopes (72 %) being presented by HLA alleles that fall within at least two different HLA supertypes. Furthermore, about 52 % of identified epitopes were conserved when the respective sequences were aligned with those from 16 highly diverse P. falciparum parasite strains. In summary, we have identified a number of conserved epitopes, immune responses to which could be effective against multiple P. falciparum parasite strains in genetically diverse populations.
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Affiliation(s)
- Maria Belmonte
- Malaria Department, Naval Medical Research Center, MD, USA; Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA
| | - Harini Ganeshan
- Malaria Department, Naval Medical Research Center, MD, USA; Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA
| | - Jun Huang
- Malaria Department, Naval Medical Research Center, MD, USA; Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA
| | - Arnel Belmonte
- Malaria Department, Naval Medical Research Center, MD, USA; GDIT, MD 20817, USA
| | - Sandra Inoue
- Malaria Department, Naval Medical Research Center, MD, USA; GDIT, MD 20817, USA
| | - Rachel Velasco
- Malaria Department, Naval Medical Research Center, MD, USA; GDIT, MD 20817, USA
| | - Neda Acheampong
- Malaria Department, Naval Medical Research Center, MD, USA; GDIT, MD 20817, USA
| | - Ebenezer Addo Ofori
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana
| | - Kwadwo Akyea-Mensah
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana
| | - Augustina Frimpong
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana
| | - Nana Aba Ennuson
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana
| | - Abena Fremaah Frempong
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana
| | - Eric Kyei-Baafour
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana
| | - Linda Eva Amoah
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana
| | - Kimberly Edgel
- Malaria Department, Naval Medical Research Center, MD, USA
| | - Bjoern Peters
- La Jolla Institute for Immunology, La Jolla, CA, USA
| | | | - Kwadwo Asamoah Kusi
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana.
| | - Martha Sedegah
- Malaria Department, Naval Medical Research Center, MD, USA
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Kusi KA, Ofori EA, Akyea-Mensah K, Kyei-Baafour E, Frimpong A, Ennuson NA, Belmonte M, Ganeshan H, Huang J, Amoah LE, Villasante E, Sedegah M. Towards large-scale identification of HLA-restricted T cell epitopes from four vaccine candidate antigens in a malaria endemic community in Ghana. Vaccine 2021; 40:757-764. [PMID: 34969544 DOI: 10.1016/j.vaccine.2021.12.042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 12/06/2021] [Accepted: 12/16/2021] [Indexed: 11/24/2022]
Abstract
Sterile protection against clinical malaria has been achieved in animal models and experimental human challenge studies involving immunization with radiation attenuated Plasmodium falciparum sporozoite vaccines as well as by live sporozoites under chloroquine prophylaxis. Parasite-specific IFN-γ and granzyme B-secreting CD8 + T cells have been identified as key mediators of protection. Although the exact parasite targets of protective CD8 + T cell responses are not fully defined, responses against a handful of vaccine candidate antigens have been associated with protection. Identifying the T cell targets in these antigens will facilitate the development of simpler, cost-effective, and efficacious next generation multi-epitope vaccines. The aim of this study was to identify immunodominant portions of four malaria vaccine candidate antigens using peripheral blood mononuclear cells (PBMCs) from adults with life-long exposure to malaria parasites. Cryopreserved PBMCs from 291 HLA-typed subjects were stimulated with pools of overlapping 15mer peptides spanning the entire sequences of P. falciparum circumsporozoite protein (CSP, 9 pools), apical membrane antigen 1 (AMA1, 12 pools), thrombospondin related anonymous protein (TRAP, 6 pools) and cell traversal for ookinetes and sporozoites (CelTOS, 4 pools) in FluoroSpot assays. 125 of 291 subjects made IFN-γ responses to 30 of the 31 peptide pools tested and 22 of 291 made granzyme B responses, with 20 making dual responses. The most frequent responses were to the CSP C-terminal region and the least frequent responses were to TRAP and CelTOS. There was no association between FluoroSpot responses and active malaria infection, detected by either microscopy, RDT, or PCR. In conclusion, CSP and AMA1 have relatively higher numbers of epitopes that trigger IFN-γ and granzyme B-secreting T cells in adults with life-long malaria parasite exposure compared to the other two antigens tested, and highlights the continued relevance of these two antigens as vaccine candidates.
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Affiliation(s)
- Kwadwo Asamoah Kusi
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana.
| | - Ebenezer Addo Ofori
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana
| | - Kwadwo Akyea-Mensah
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana
| | - Eric Kyei-Baafour
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana
| | - Augustina Frimpong
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana
| | - Nana Aba Ennuson
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana
| | - Maria Belmonte
- Malaria Department, Naval Medical Research Center, MD, USA; Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA
| | - Harini Ganeshan
- Malaria Department, Naval Medical Research Center, MD, USA; Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA
| | - Jun Huang
- Malaria Department, Naval Medical Research Center, MD, USA; Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA
| | - Linda Eva Amoah
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana
| | | | - Martha Sedegah
- Malaria Department, Naval Medical Research Center, MD, USA
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Nlinwe ON, Ofori EA, Akyea-Mensah K, Kyei-Baafour E, Ganeshan H, Belmonte M, Peters B, Villasante E, Sedegah M, Kusi KA. Comparative analysis of the ex vivo IFN-gamma responses to CD8+ T cell epitopes within allelic forms of PfAMA1 in subjects with natural exposure to malaria. PLoS One 2021; 16:e0257219. [PMID: 34506564 DOI: 10.1371/journal.pone.0257219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 08/25/2021] [Indexed: 11/20/2022] Open
Abstract
Antigen polymorphisms in essential malarial antigens are a key challenge to the design and development of broadly effective malaria vaccines. The effect of polymorphisms on antibody responses is fairly well studied while much fewer studies have assessed this for T cell responses. This study investigated the effect of allelic polymorphisms in the malarial antigen apical membrane antigen 1 (AMA1) on ex vivo T cell-specific IFN-γ responses in subjects with lifelong exposure to malaria. Human leukocyte antigen (HLA) class I-restricted peptides from the 3D7 clone AMA1 were bioinformatically predicted and those with variant amino acid positions used to select corresponding allelic sequences from the 7G8, FVO, FC27 and tm284 parasite strains. A total of 91 AMA1 9-10mer peptides from the five parasite strains were identified, synthesized, grouped into 42 allele sets and used to stimulate PBMCs from seven HLA class 1-typed subjects in IFN-γ ELISpot assays. PBMCs from four of the seven subjects (57%) made positive responses to 18 peptides within 12 allele sets. Fifty percent of the 18 positive peptides were from the 3D7 parasite variant. Amino acid substitutions that were associated with IFN-γ response abrogation were more frequently found at positions 1 and 6 of the tested peptides, but substitutions did not show a clear pattern of association with response abrogation. Thus, while we show some evidence of polymorphisms affecting T cell response induction, other factors including TCR recognition of HLA-peptide complexes may also be at play.
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Ofori EA, Tetteh JKA, Frimpong A, Ganeshan H, Belmonte M, Peters B, Villasante E, Sedegah M, Ofori MF, Kusi KA. Comparison of the impact of allelic polymorphisms in PfAMA1 on the induction of T Cell responses in high and low malaria endemic communities in Ghana. Malar J 2021; 20:367. [PMID: 34507582 PMCID: PMC8431259 DOI: 10.1186/s12936-021-03900-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 08/28/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Malaria eradication requires a combined effort involving all available control tools, and these efforts would be complemented by an effective vaccine. The antigen targets of immune responses may show polymorphisms that can undermine their recognition by immune effectors and hence render vaccines based on antigens from a single parasite variant ineffective against other variants. This study compared the influence of allelic polymorphisms in Plasmodium falciparum apical membrane antigen 1 (PfAMA1) peptide sequences from three strains of P. falciparum (3D7, 7G8 and FVO) on their function as immunodominant targets of T cell responses in high and low malaria transmission communities in Ghana. METHODS Peripheral blood mononuclear cells (PBMCs) from 10 subjects from a high transmission area (Obom) and 10 subjects from a low transmission area (Legon) were tested against 15 predicted CD8 + T cell minimal epitopes within the PfAMA1 antigen of multiple parasite strains using IFN-γ ELISpot assay. The peptides were also tested in similar assays against CD8 + enriched PBMC fractions from the same subjects in an effort to characterize the responding T cell subsets. RESULTS In assays using unfractionated PBMCs, two subjects from the high transmission area, Obom, responded positively to four (26.7%) of the 15 tested peptides. None of the Legon subject PBMCs yielded positive peptide responses using unfractionated PBMCs. In assays with CD8 + enriched PBMCs, three subjects from Obom made positive recall responses to six (40%) of the 15 tested peptides, while only one subject from Legon made a positive recall response to a single peptide. Overall, 5 of the 20 study subjects who had positive peptide-specific IFN-γ recall responses were from the high transmission area, Obom. Furthermore, while subjects from Obom responded to peptides in PfAMA1 from multiple parasite strains, one subject from Legon responded to a peptide from 3D7 strain only. CONCLUSIONS The current data demonstrate the possibility of a real effect of PfAMA1 polymorphisms on the induction of T cell responses in malaria exposed subjects, and this effect may be more pronounced in communities with higher parasite exposure.
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Affiliation(s)
- Ebenezer A Ofori
- West Africa Centre for Cell Biology of Infectious Pathogens, Department of Biochemistry, Cell and Molecular Biology, College of Basic and Applied Sciences, University of Ghana, Legon, Accra, Ghana.,Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Accra, Ghana
| | - John K A Tetteh
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Accra, Ghana
| | - Augustina Frimpong
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Accra, Ghana
| | - Harini Ganeshan
- Malaria Department, Naval Medical Research Center, Silver Spring, USA.,Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA
| | - Maria Belmonte
- Malaria Department, Naval Medical Research Center, Silver Spring, USA.,Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA
| | - Bjoern Peters
- La Jolla Institute for Allergy and Immunology, La Jolla, CA, USA
| | - Eileen Villasante
- Malaria Department, Naval Medical Research Center, Silver Spring, USA
| | - Martha Sedegah
- Malaria Department, Naval Medical Research Center, Silver Spring, USA
| | - Michael F Ofori
- West Africa Centre for Cell Biology of Infectious Pathogens, Department of Biochemistry, Cell and Molecular Biology, College of Basic and Applied Sciences, University of Ghana, Legon, Accra, Ghana.,Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Accra, Ghana
| | - Kwadwo A Kusi
- West Africa Centre for Cell Biology of Infectious Pathogens, Department of Biochemistry, Cell and Molecular Biology, College of Basic and Applied Sciences, University of Ghana, Legon, Accra, Ghana. .,Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Accra, Ghana.
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